Yeah, that really sucks. We deal with crows around here all the time. We are midway on their flight path from their nests to the local shopping mall where they do all of their dumpster diving. It seems our neighborhood is one of their favorite stops on their morning and evening commutes - sometimes we have what must be literally thousands of the damn things hanging out.
Shooting them is not the answer. You'll run out of ammo before you run out of crows. That, and they are remarkably tough to kill. And, as others have noted, remarkably intelligent - and vengeful. When I was still young and stupid (o.k.,
more stupid) I made the mistake of shooting them in my yard. The only result was that, for a time, my wife, two sons, and I could not sit out in the back yard - we would get attacked by crows. Real deal, Bodega Bay style. Literally pecking at our heads.
So, I think "defense is the best offense". Cover your stuff, don't give them places to perch, and that kind of thing. Here in the PNW, seagulls are an even bigger problem, at least around our docks. I'm not sure you've seen this, or if it would even be acceptable, but here is how we keep seagulls off of our stuff:
Granted, you can't cover your boat like this, but using something like this to reduce the other places they can land seems to be effective. Kinda ugly, though...